ventilator due to the high susceptibility of the premature infant to lung injury from conventional ventilation. Breath delivery The vibrations are created by an electromagnetic valve that controls a piston. The resulting vibrations are similar to those produced by a stereo speaker. The height of the vibrational wave is the amplitude. Higher amplitudes create greater pressure fluctuations which move more gas with each vibration. The number of vibrations per minute is the frequency. One Hertz equals 60 cycles per minute. The higher amplitudes at lower frequencies will cause the greatest fluctuation in pressure and move the most gas. Altering the % inspiratory time (T%i) changes the proportion of the time in which the vibration or sound wave is above the baseline versus below it. Increasing the % Inspiratory Time will also increase the volume of gas moved or tidal volume. Decreasing the frequency, increasing the amplitude, and increasing the % inspiratory time will all increase tidal volume and eliminate CO2. Increasing the tidal volume will also tend to increase the mean airway pressure. Settings and measurements Bias flow The bias flow controls and indicates the rate of continuous flow of humidified blended gas through the patient circuit. The control knob is a 15-turn pneumatic valve which increases flow as it is turned. Mean pressure adjust The mean pressure adjust setting adjusts the mean airway pressure (PAW) by controlling the resistance of the airway pressure control valve. The mean airway pressure will change and requires the mean pressure adjust to be adjusted when the following settings are changed: Frequency (Hertz) % Inspiratory time Power and Δp change Piston centering During high-frequency oscillatory ventilation (HFOV), PAW is the primary variable affecting oxygenation and is set independent of other variables on the oscillator. Because distal airway pressure changes during HFOV are minimal, the PAW during HFOV can be viewed in a manner similar to the PEEP level in conventional ventilation. The optimal PAW can be considered as a compromise between maximal lung recruitment and minimal overdistention. Mean pressure limit The mean pressure limit controls the limit above which proximal PAW cannot be increased by setting the control pressure of the pressure limit valve. The mean pressure limit range is 10-45 cmH2O. ΔP and amplitude The power setting is set as amplitude to establish a measured change of pressure (ΔP). Amplitude/Power is a setting which determines the amount of power that is driving the